A variety of stationary exercise machines are known to the art. Examples of such machines include stationary rowing machines and stationary bicycles. These machines typically simulate a common human activity, such as rowing or bicycling. Prior art machines typically lack in adaptability to specialized exercise needs, and in flexibility to accommodate properly to the physical size of the user.
Rowing, for example, is usually a combined upper and lower body exercise, especially where a sliding seat is provided for the rower. Rowing absorbs work from a large muscle mass, including the major muscles of the arms, torso and legs, in a bilaterally symmetrical, rhythmic pattern of movement. A bilaterally symmetric pattern of movement is one that is identical and simultaneous between the sides of the body. Rowing is generally considered to be an excellent exercise, both for cardiovascular benefits as well as overall conditioning. However, rowing has disadvantages for some individuals, such as patients undergoing rehabilitative therapy, who cannot match the range of movement required by the exercise. The rigid definition of the rowing movement does not allow the exerciser to change muscle sets to meet the total intensity level required or to compensate for limited mobility in certain joints.
Another disadvantage of rowing is a high perceived effort required to achieve a given workout intensity level. This high perceived effort results from a number of factors. Rowing imposes an extreme hip and torso flexion at the beginning of each power stroke. The extreme flexion increases intrathoracic pressures which affect cardiac output and make breathing more difficult. Moreover, the workload is imposed in an on and off pattern, on during the expanding power stroke and off during the relaxation phase. The portion of the total workload concentrated in the power strokes is thus large. In addition, rowing imposes a substantial amount of lower back stress on the user.
Stationary bicycles avoid the stop and start sensation of a rowing machine. However, stationary bicycles have their own disadvantages. Cycling does not distribute the workload, but confines it to the leg muscles. Obviously, the user cannot change muscle sets or the pattern of the exercise and maintain the same overall intensity of exercise. Also, stationary bicycles have typically adapted perch type seats, influenced by conventional safety bicycles, as an exercise position. This position is not usually comfortable to the infrequent cyclist, and tends to contribute to a feeling of instability of the machines. The perch type saddle contributes to saddle sores and to a relative lack of stability of the machine.
A handful of prior art devices have attempted to combine a rowing or other type of upper body exercise with a cycling exercise. One prior art device, taught in U.S. Pat. No. 4,188,030, issued Feb. 12, 1980, provides a stationary bicycle with a pair of exercise arms which are linked to the mechanical movement of the cycling exercise. A user can employ the arms or the cycling pedals to drive the movement. Resistance is applied to the movement to increase the workload. However, linkage of the mechanical movements rigidly defines the range of movement of the exercises. In addition, the device taught is substantially a conventional stationary bicycle which has exercise arms. It retains the perch position common to conventional exercise cycles.
Another prior art device is taught in U.S. Pat. No. 4,729,559, issued on Mar. 8, 1988. It includes exercise arms which are mechanically independent of a cycling exercise. However, the device does not include a way of determining the workload distributed between the cycling exercise and the upper body exercise. The device retains perch type seating common to other stationary bicycles.
Exercise, when appropriately administered, can elicit any one, or a combination, of many beneficial effects. These effects include increased cardiovascular efficiency and endurance, muscle strength and tone, and control of weight. Three different measurements of an individual's exercise may be made which relate to attaining the beneficial effects. These include a measurement of intensity comprising the level of power output of the individual, duration of an individualIs bout of exercise and frequency of bouts of exercise. Intensity and duration may be used as factors in a calculation of total work done or energy expended in a particular bout, i.e., calories. The above noted benefits are enjoyed only when exercise is persisted in at appropriate intensity levels.
U.S. patent application Ser. No. 07/252,169 filed Sep. 30, 1988, assigned to the assignee of the present invention, proposed an exercise machine solving many of the above problems. The exercise machine was directed to maintaining a higher degree of perceived comfort and ease, contributing to greater exercise frequency, while guiding the user in maintaining an appropriate level of intensity in individual bouts. The exercise device provides a cycling action for exercise of the lower body and a pair of exercise arms for upper body exercise. By providing for upper and lower body exercise, the workload on the user is distributed over a large number of muscle groups and muscle actions.
The upper body exercise provided by the exercise machine includes a mechanical movement which applies resistance to each exercise arm in both directions of movement of an exercise arm. In addition, the arms can be moved entirely independently of one another, and can be moved for only a fraction of their overall travel. The mechanical movement allows "unilateral reciprocation" involving movement of the arms oppositely in a rhythmic pattern. The movement also permits "independent unilateral movement", in which no particular relationship exists between movements of the arm and, in fact, in which one arm may remain motionless. A load is applied to the mechanical movement by mechanical connection of the movement to an electrical generator, to which a resistive load is applied.
The mechanical apparatus for upper body exercise in the exercise machine described in U.S. application Ser. No. 07/252,169 generated single directional rotational motion in a predetermined direction from reciprocating movement. The mechanism includes a frame, first and second wheels supported for rotation at spaced locations on the frame, a belt coupling the first and second wheels for rotation, a first wheel cluster including a plurality of wheels engaging the belt for driving the belt in a single direction, a second wheel cluster including a plurality of wheels engaging the belt for driving the belt in the single direction, where the first and second wheel clusters are supported on a reciprocable carrier for movement substantially parallel to the belt between the first and second wheels. Unlike a conventional connection of a crank arm to a pulley, no dead points exist in the mechanism. Where a crank arm is connected off center to a pulley, two points occur during rotation of the pulley where force applied to the crank arm, in either direction, will not contribute to rotation of the pulley. The apparatus of the application has no such problem.
However, use of a flexible belt, such as a chain, can produce an unpleasant jerking sensation to the user stemming from chordal action of the chain. The jerking sensation is a byproduct of changing velocities of sections or linkages of a belt or chain associated with changes in flexing or bending of the section. Chordal action can be eliminated if the chain can be replaced by a system of gears.